1. Field of the Invention
The present invention relates to a display device capable of displaying an image to each of a plurality of viewpoints, its driving method, a terminal device, and a display panel. More specifically, the present invention relates to a display device capable of providing high quality display, its driving method, a terminal device, and a display panel.
2. Description of the Related Art
Owing to the recent technical developments, display panels are used in various places by being loaded not only to large-scale terminal devices such as monitors and television receiver sets but also to medium-scale terminal devices such as notebook-type personal computers, cash dispensers, and vending machines, and to small-scale terminal devices such as personal TVs, PDAs (Personal Digital Assistances), portable telephones, and portable game machines. Particularly, liquid crystal display devices using liquid crystal have many advantages such as being thin in thickness, light in weight, small in size, and low in terms of power consumption, so that those are loaded to various terminal devices. With a current display device, same display contents as those when viewed from a front direction can be observed from places other than the front direction. However, a display device with which different images can be observed depending on the viewpoints, i.e., depending on the positions from which observers views the display, has also been developed. Such device is expected to grow as a display device of next generation. As an example of the device capable of displaying different images to each of a plurality of viewpoints, there is a stereoscopic image display device. Particularly, a lenticular lens type and parallax barrier type have been proposed as a stereoscopic image display system that requires no special eye glasses.
The inventors of the present invention have zealously conducted studies on a plural-viewpoint display device having an optical element such as a lenticular lens for separating images so as to develop a method for achieving high quality images (see Japanese Unexamined Patent Publication 2005-208567 (FIG. 37): Patent Document 1, for example). FIG. 34 is a plan view showing a display panel of an image display device depicted in Patent Document 1. As shown in FIG. 34, an aperture 1075 of the display panel is in a shape including a trapezoid on a plan view. Specifically, the aperture 1075 is in a hexagonal shape in which a bilateral-symmetric trapezoid and a rectangle whose long side has an equal length with the length of a lower bottom of the trapezoid are placed in such a manner that a lower bottom of the trapezoid and a long side of the rectangle are in contact with each other.
Assuming that the longitudinal direction of cylindrical lenses 1003a that configure a lenticular lens is a vertical direction 1011 and an arranging direction thereof is a lateral direction 1012, the shape of the aperture 1075 is laterally symmetrical with respect to a segment extending in the vertical direction 1011. Further, there is a pair of sides that are tilted in opposite directions with respect to the vertical direction 1011 from each other, having same angles between the extending direction and the vertical direction 1011. As a result, in the lateral direction 1012, the end positions of the apertures 1075 of the display panel and the optical axis positions of the cylindrical lenses 1003a become relatively shifted in the vertical direction 1011.
Further, the apertures 1075 neighboring to each other in the vertical direction 1011 are arranged to be line-symmetrical with respect to a segment extending in the lateral direction 1012. Further, the apertures 1075 neighboring to each other in the lateral direction 1012 are arranged to be point-symmetrical with respect to an intersection point between a segment connecting between the middle point of both ends in the vertical direction 1011 and a segment connecting between the middle points of both ends in the lateral direction 102. Thus, the width of the aperture 1075 in the vertical direction 1011 together with the neighboring aperture 1075 in the lateral direction 1012 is substantially constant regardless of the positions in the lateral direction 1012.
A light shielding part 1076 is provided only at an edge of a pixel extending in the lateral direction 1012 but not provided at edges of the pixel sloping towards the vertical direction 1011. The apertures 1075 neighboring to each other in the lateral direction 1012 are sectioned by wirings 1070, and shielded from light by the wirings 1070.
In the display device depicted in Patent Document 1, the aperture of each pixel is formed in a shape including a trapezoid, and the apertures of the neighboring pixels are arranged to be in a point-symmetrical or line-symmetrical relation. Thereby, the numerical aperture in the vertical direction 1011 can be made substantially constant at arbitrary positions in the lateral direction 1012. As a result, deterioration in the display qualities caused due to the light-shielding areas can be prevented completely.
Further, as another example of the device capable of displaying different images for each of a plurality of viewpoints, there has been developed a plural-image simultaneous displaying device that is capable of displaying a plurality of different images for a plurality of viewpoints simultaneously (see Japanese Unexamined Patent Publication 06-332354: Patent Document 2, for example). This is a display that displays different images for each observing direction simultaneously under a same condition by utilizing an image allotting function of a lenticular lens. This makes it possible with a single display device to provide different images from each other simultaneously to a plurality of observers that are located at a different position from each other with respect to the display device.
As described, a great number of plural-viewpoint display devices have been studied, and the aperture shapes of the pixels suited for those display devices have been proposed.
However, the techniques described above have following issues. That is, for increasing the display qualities while using thin film transistors, it is difficult with the conventional pixel structure to improve the numerical aperture while maintaining the above-described aperture shape.